A number of ruthenate compounds are known in the art to be useful as anti-tumor compounds. See e.g., U.S. Pat. No. 4,843,069, PCT Publication No. WO 9736595, and US Application Publication No. 2005032801. In particular, the compounds ruthenium complex salt indazolium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (KP1099) and sodium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (KP1339) have been shown to be highly potent in inducing apoptosis in a broad spectrum of cancer cells. See e.g., Kapitza et al., J. Cancer Res. Clin. Oncol., 131(2):101-10 (2005).
The existing methods of making sodium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (KP1339) in the art are cumbersome. For example, W. Peti et al, Eur. J. Inorg. Chem. 1999, 1551-1555 discloses the following synthesis scheme.
In this method, due to the limited solubility of the tetramethylammoniumchloride salt, in the second step high volumes of solvent are necessary. The efficiency of the process is low. There is need for improved alternative synthesis process.